| Message ID | 20250224232012.GA7359@templeofstupid.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Commit | b565c3e97c561dbe8a154befd7a0f370c1c5bb9d |
| Delegated to: | Matthieu Baerts |
| Headers | show |
| Series | [v2] mptcp: fix 'scheduling while atomic' in mptcp_pm_nl_append_new_local_addr | expand |
| Context | Check | Description |
|---|---|---|
| matttbe/build | success | Build and static analysis OK |
| matttbe/checkpatch | warning | total: 0 errors, 1 warnings, 0 checks, 42 lines checked |
| matttbe/shellcheck | success | MPTCP selftests files have not been modified |
| matttbe/KVM_Validation__normal | success | Success! ✅ |
| matttbe/KVM_Validation__debug | success | Success! ✅ |
| matttbe/KVM_Validation__btf-normal__only_bpftest_all_ | success | Success! ✅ |
| matttbe/KVM_Validation__btf-debug__only_bpftest_all_ | success | Success! ✅ |
Hi Krister,
Thank you for your modifications, that's great!
Our CI did some validations and here is its report:
- KVM Validation: normal: Success! ✅
- KVM Validation: debug: Success! ✅
- KVM Validation: btf-normal (only bpftest_all): Success! ✅
- KVM Validation: btf-debug (only bpftest_all): Success! ✅
- Task: https://github.com/multipath-tcp/mptcp_net-next/actions/runs/13510193894
Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/b89b385a81ca
Patchwork: https://patchwork.kernel.org/project/mptcp/list/?series=937276
If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:
$ cd [kernel source code]
$ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
--pull always mptcp/mptcp-upstream-virtme-docker:latest \
auto-normal
For more details:
https://github.com/multipath-tcp/mptcp-upstream-virtme-docker
Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)
Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (NGI0 Core)
Hi Krister, On 25/02/2025 00:20, Krister Johansen wrote: > If multiple connection requests attempt to create an implicit mptcp > endpoint in parallel, more than one caller may end up in > mptcp_pm_nl_append_new_local_addr because none found the address in > local_addr_list during their call to mptcp_pm_nl_get_local_id. In this > case, the concurrent new_local_addr calls may delete the address entry > created by the previous caller. These deletes use synchronize_rcu, but > this is not permitted in some of the contexts where this function may be > called. During packet recv, the caller may be in a rcu read critical > section and have preemption disabled. Thank you for this patch, and for having taken the time to analyse the issue! > An example stack: > > BUG: scheduling while atomic: swapper/2/0/0x00000302 > > Call Trace: > <IRQ> > dump_stack_lvl+0x76/0xa0 > dump_stack+0x10/0x20 > __schedule_bug+0x64/0x80 > schedule_debug.constprop.0+0xdb/0x130 > __schedule+0x69/0x6a0 > schedule+0x33/0x110 > schedule_timeout+0x157/0x170 > wait_for_completion+0x88/0x150 > __wait_rcu_gp+0x150/0x160 > synchronize_rcu+0x12d/0x140 > mptcp_pm_nl_append_new_local_addr+0x1bd/0x280 > mptcp_pm_nl_get_local_id+0x121/0x160 > mptcp_pm_get_local_id+0x9d/0xe0 > subflow_check_req+0x1a8/0x460 > subflow_v4_route_req+0xb5/0x110 > tcp_conn_request+0x3a4/0xd00 > subflow_v4_conn_request+0x42/0xa0 > tcp_rcv_state_process+0x1e3/0x7e0 > tcp_v4_do_rcv+0xd3/0x2a0 > tcp_v4_rcv+0xbb8/0xbf0 > ip_protocol_deliver_rcu+0x3c/0x210 > ip_local_deliver_finish+0x77/0xa0 > ip_local_deliver+0x6e/0x120 > ip_sublist_rcv_finish+0x6f/0x80 > ip_sublist_rcv+0x178/0x230 > ip_list_rcv+0x102/0x140 > __netif_receive_skb_list_core+0x22d/0x250 > netif_receive_skb_list_internal+0x1a3/0x2d0 > napi_complete_done+0x74/0x1c0 > igb_poll+0x6c/0xe0 [igb] > __napi_poll+0x30/0x200 > net_rx_action+0x181/0x2e0 > handle_softirqs+0xd8/0x340 > __irq_exit_rcu+0xd9/0x100 > irq_exit_rcu+0xe/0x20 > common_interrupt+0xa4/0xb0 > </IRQ> Detail: if possible, next time, do not hesitate to resolve the addresses, e.g. using: ./scripts/decode_stacktrace.sh > This problem seems particularly prevalent if the user advertises an > endpoint that has a different external vs internal address. In the case > where the external address is advertised and multiple connections > already exist, multiple subflow SYNs arrive in parallel which tends to > trigger the race during creation of the first local_addr_list entries > which have the internal address instead. > > Fix by skipping the replacement of an existing implicit local address if > called via mptcp_pm_nl_get_local_id. The v2 looks good to me: Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> I'm going to apply it in our MPTCP tree, but this patch can also be directly applied in the net tree directly, not to delay it by one week if preferred. If not, I can re-send it later on. Cheers, Matt
Hi Matt, Thanks for the review! On Tue, Feb 25, 2025 at 06:52:45PM +0100, Matthieu Baerts wrote: > On 25/02/2025 00:20, Krister Johansen wrote: > > If multiple connection requests attempt to create an implicit mptcp > > endpoint in parallel, more than one caller may end up in > > mptcp_pm_nl_append_new_local_addr because none found the address in > > local_addr_list during their call to mptcp_pm_nl_get_local_id. In this > > case, the concurrent new_local_addr calls may delete the address entry > > created by the previous caller. These deletes use synchronize_rcu, but > > this is not permitted in some of the contexts where this function may be > > called. During packet recv, the caller may be in a rcu read critical > > section and have preemption disabled. > > Thank you for this patch, and for having taken the time to analyse the > issue! > > > An example stack: > > > > BUG: scheduling while atomic: swapper/2/0/0x00000302 > > > > Call Trace: > > <IRQ> > > dump_stack_lvl+0x76/0xa0 > > dump_stack+0x10/0x20 > > __schedule_bug+0x64/0x80 > > schedule_debug.constprop.0+0xdb/0x130 > > __schedule+0x69/0x6a0 > > schedule+0x33/0x110 > > schedule_timeout+0x157/0x170 > > wait_for_completion+0x88/0x150 > > __wait_rcu_gp+0x150/0x160 > > synchronize_rcu+0x12d/0x140 > > mptcp_pm_nl_append_new_local_addr+0x1bd/0x280 > > mptcp_pm_nl_get_local_id+0x121/0x160 > > mptcp_pm_get_local_id+0x9d/0xe0 > > subflow_check_req+0x1a8/0x460 > > subflow_v4_route_req+0xb5/0x110 > > tcp_conn_request+0x3a4/0xd00 > > subflow_v4_conn_request+0x42/0xa0 > > tcp_rcv_state_process+0x1e3/0x7e0 > > tcp_v4_do_rcv+0xd3/0x2a0 > > tcp_v4_rcv+0xbb8/0xbf0 > > ip_protocol_deliver_rcu+0x3c/0x210 > > ip_local_deliver_finish+0x77/0xa0 > > ip_local_deliver+0x6e/0x120 > > ip_sublist_rcv_finish+0x6f/0x80 > > ip_sublist_rcv+0x178/0x230 > > ip_list_rcv+0x102/0x140 > > __netif_receive_skb_list_core+0x22d/0x250 > > netif_receive_skb_list_internal+0x1a3/0x2d0 > > napi_complete_done+0x74/0x1c0 > > igb_poll+0x6c/0xe0 [igb] > > __napi_poll+0x30/0x200 > > net_rx_action+0x181/0x2e0 > > handle_softirqs+0xd8/0x340 > > __irq_exit_rcu+0xd9/0x100 > > irq_exit_rcu+0xe/0x20 > > common_interrupt+0xa4/0xb0 > > </IRQ> > Detail: if possible, next time, do not hesitate to resolve the > addresses, e.g. using: ./scripts/decode_stacktrace.sh My apologies for the oversight here. This is the decoded version of the stack: Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:117 (discriminator 1)) dump_stack (lib/dump_stack.c:124) __schedule_bug (kernel/sched/core.c:5943) schedule_debug.constprop.0 (arch/x86/include/asm/preempt.h:33 kernel/sched/core.c:5970) __schedule (arch/x86/include/asm/jump_label.h:27 include/linux/jump_label.h:207 kernel/sched/features.h:29 kernel/sched/core.c:6621) schedule (arch/x86/include/asm/preempt.h:84 kernel/sched/core.c:6804 kernel/sched/core.c:6818) schedule_timeout (kernel/time/timer.c:2160) wait_for_completion (kernel/sched/completion.c:96 kernel/sched/completion.c:116 kernel/sched/completion.c:127 kernel/sched/completion.c:148) __wait_rcu_gp (include/linux/rcupdate.h:311 kernel/rcu/update.c:444) synchronize_rcu (kernel/rcu/tree.c:3609) mptcp_pm_nl_append_new_local_addr (net/mptcp/pm_netlink.c:966 net/mptcp/pm_netlink.c:1061) mptcp_pm_nl_get_local_id (net/mptcp/pm_netlink.c:1164) mptcp_pm_get_local_id (net/mptcp/pm.c:420) subflow_check_req (net/mptcp/subflow.c:98 net/mptcp/subflow.c:213) subflow_v4_route_req (net/mptcp/subflow.c:305) tcp_conn_request (net/ipv4/tcp_input.c:7216) subflow_v4_conn_request (net/mptcp/subflow.c:651) tcp_rcv_state_process (net/ipv4/tcp_input.c:6709) tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1934) tcp_v4_rcv (net/ipv4/tcp_ipv4.c:2334) ip_protocol_deliver_rcu (net/ipv4/ip_input.c:205 (discriminator 1)) ip_local_deliver_finish (include/linux/rcupdate.h:813 net/ipv4/ip_input.c:234) ip_local_deliver (include/linux/netfilter.h:314 include/linux/netfilter.h:308 net/ipv4/ip_input.c:254) ip_sublist_rcv_finish (include/net/dst.h:461 net/ipv4/ip_input.c:580) ip_sublist_rcv (net/ipv4/ip_input.c:640) ip_list_rcv (net/ipv4/ip_input.c:675) __netif_receive_skb_list_core (net/core/dev.c:5583 net/core/dev.c:5631) netif_receive_skb_list_internal (net/core/dev.c:5685 net/core/dev.c:5774) napi_complete_done (include/linux/list.h:37 include/net/gro.h:449 include/net/gro.h:444 net/core/dev.c:6114) igb_poll (drivers/net/ethernet/intel/igb/igb_main.c:8244) igb __napi_poll (net/core/dev.c:6582) net_rx_action (net/core/dev.c:6653 net/core/dev.c:6787) handle_softirqs (kernel/softirq.c:553) __irq_exit_rcu (kernel/softirq.c:588 kernel/softirq.c:427 kernel/softirq.c:636) irq_exit_rcu (kernel/softirq.c:651) common_interrupt (arch/x86/kernel/irq.c:247 (discriminator 14)) </IRQ> > > This problem seems particularly prevalent if the user advertises an > > endpoint that has a different external vs internal address. In the case > > where the external address is advertised and multiple connections > > already exist, multiple subflow SYNs arrive in parallel which tends to > > trigger the race during creation of the first local_addr_list entries > > which have the internal address instead. > > > > Fix by skipping the replacement of an existing implicit local address if > > called via mptcp_pm_nl_get_local_id. > The v2 looks good to me: > > Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org> > > I'm going to apply it in our MPTCP tree, but this patch can also be > directly applied in the net tree directly, not to delay it by one week > if preferred. If not, I can re-send it later on. Thanks, I'd be happy to send it to net directly now that it has your blessing. Would you like me to modify the call trace in the commit message to match the decoded one that I included above before I send it to net? Thanks, -K
Hi Krister, On 25/02/2025 20:29, Krister Johansen wrote: > Hi Matt, > Thanks for the review! > > On Tue, Feb 25, 2025 at 06:52:45PM +0100, Matthieu Baerts wrote: >> On 25/02/2025 00:20, Krister Johansen wrote: >>> If multiple connection requests attempt to create an implicit mptcp >>> endpoint in parallel, more than one caller may end up in >>> mptcp_pm_nl_append_new_local_addr because none found the address in >>> local_addr_list during their call to mptcp_pm_nl_get_local_id. In this >>> case, the concurrent new_local_addr calls may delete the address entry >>> created by the previous caller. These deletes use synchronize_rcu, but >>> this is not permitted in some of the contexts where this function may be >>> called. During packet recv, the caller may be in a rcu read critical >>> section and have preemption disabled. >> >> Thank you for this patch, and for having taken the time to analyse the >> issue! >> >>> An example stack: (...) >> Detail: if possible, next time, do not hesitate to resolve the >> addresses, e.g. using: ./scripts/decode_stacktrace.sh > > My apologies for the oversight here. This is the decoded version of the > stack: No problem, thanks for the decoded version! (...) >> I'm going to apply it in our MPTCP tree, but this patch can also be >> directly applied in the net tree directly, not to delay it by one week >> if preferred. If not, I can re-send it later on. > > Thanks, I'd be happy to send it to net directly now that it has your > blessing. Would you like me to modify the call trace in the commit > message to match the decoded one that I included above before I send it > to net? Sorry, I forgot to mention that this bit was for the net maintainers. Typically, trivial patches and small fixes related to MPTCP can go directly to net. No need for you to re-send it. If the net maintainers prefer me to send it later with other patches (if any), I will update the call trace, no problem! Cheers, Matt
Hi Matt, On Tue, Feb 25, 2025 at 10:41:55PM +0100, Matthieu Baerts wrote: > On 25/02/2025 20:29, Krister Johansen wrote: > > On Tue, Feb 25, 2025 at 06:52:45PM +0100, Matthieu Baerts wrote: > >> I'm going to apply it in our MPTCP tree, but this patch can also be > >> directly applied in the net tree directly, not to delay it by one week > >> if preferred. If not, I can re-send it later on. > > > > Thanks, I'd be happy to send it to net directly now that it has your > > blessing. Would you like me to modify the call trace in the commit > > message to match the decoded one that I included above before I send it > > to net? > > Sorry, I forgot to mention that this bit was for the net maintainers. > Typically, trivial patches and small fixes related to MPTCP can go > directly to net. > > No need for you to re-send it. If the net maintainers prefer me to send > it later with other patches (if any), I will update the call trace, no > problem! Thanks for clarifying. I'll hold off on sending anything further and will either let the net maintainers pick this up, or have you send it with your next batch of patches. Thanks again! -K
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index c0e47f4f7b1a..7868207c4e9d 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -977,7 +977,7 @@ static void __mptcp_pm_release_addr_entry(struct mptcp_pm_addr_entry *entry) static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet, struct mptcp_pm_addr_entry *entry, - bool needs_id) + bool needs_id, bool replace) { struct mptcp_pm_addr_entry *cur, *del_entry = NULL; unsigned int addr_max; @@ -1017,6 +1017,17 @@ static int mptcp_pm_nl_append_new_local_addr(struct pm_nl_pernet *pernet, if (entry->addr.id) goto out; + /* allow callers that only need to look up the local + * addr's id to skip replacement. This allows them to + * avoid calling synchronize_rcu in the packet recv + * path. + */ + if (!replace) { + kfree(entry); + ret = cur->addr.id; + goto out; + } + pernet->addrs--; entry->addr.id = cur->addr.id; list_del_rcu(&cur->list); @@ -1165,7 +1176,7 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct mptcp_addr_info *skc entry->ifindex = 0; entry->flags = MPTCP_PM_ADDR_FLAG_IMPLICIT; entry->lsk = NULL; - ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true); + ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, true, false); if (ret < 0) kfree(entry); @@ -1433,7 +1444,8 @@ int mptcp_pm_nl_add_addr_doit(struct sk_buff *skb, struct genl_info *info) } } ret = mptcp_pm_nl_append_new_local_addr(pernet, entry, - !mptcp_pm_has_addr_attr_id(attr, info)); + !mptcp_pm_has_addr_attr_id(attr, info), + true); if (ret < 0) { GENL_SET_ERR_MSG_FMT(info, "too many addresses or duplicate one: %d", ret); goto out_free;
If multiple connection requests attempt to create an implicit mptcp endpoint in parallel, more than one caller may end up in mptcp_pm_nl_append_new_local_addr because none found the address in local_addr_list during their call to mptcp_pm_nl_get_local_id. In this case, the concurrent new_local_addr calls may delete the address entry created by the previous caller. These deletes use synchronize_rcu, but this is not permitted in some of the contexts where this function may be called. During packet recv, the caller may be in a rcu read critical section and have preemption disabled. An example stack: BUG: scheduling while atomic: swapper/2/0/0x00000302 Call Trace: <IRQ> dump_stack_lvl+0x76/0xa0 dump_stack+0x10/0x20 __schedule_bug+0x64/0x80 schedule_debug.constprop.0+0xdb/0x130 __schedule+0x69/0x6a0 schedule+0x33/0x110 schedule_timeout+0x157/0x170 wait_for_completion+0x88/0x150 __wait_rcu_gp+0x150/0x160 synchronize_rcu+0x12d/0x140 mptcp_pm_nl_append_new_local_addr+0x1bd/0x280 mptcp_pm_nl_get_local_id+0x121/0x160 mptcp_pm_get_local_id+0x9d/0xe0 subflow_check_req+0x1a8/0x460 subflow_v4_route_req+0xb5/0x110 tcp_conn_request+0x3a4/0xd00 subflow_v4_conn_request+0x42/0xa0 tcp_rcv_state_process+0x1e3/0x7e0 tcp_v4_do_rcv+0xd3/0x2a0 tcp_v4_rcv+0xbb8/0xbf0 ip_protocol_deliver_rcu+0x3c/0x210 ip_local_deliver_finish+0x77/0xa0 ip_local_deliver+0x6e/0x120 ip_sublist_rcv_finish+0x6f/0x80 ip_sublist_rcv+0x178/0x230 ip_list_rcv+0x102/0x140 __netif_receive_skb_list_core+0x22d/0x250 netif_receive_skb_list_internal+0x1a3/0x2d0 napi_complete_done+0x74/0x1c0 igb_poll+0x6c/0xe0 [igb] __napi_poll+0x30/0x200 net_rx_action+0x181/0x2e0 handle_softirqs+0xd8/0x340 __irq_exit_rcu+0xd9/0x100 irq_exit_rcu+0xe/0x20 common_interrupt+0xa4/0xb0 </IRQ> This problem seems particularly prevalent if the user advertises an endpoint that has a different external vs internal address. In the case where the external address is advertised and multiple connections already exist, multiple subflow SYNs arrive in parallel which tends to trigger the race during creation of the first local_addr_list entries which have the internal address instead. Fix by skipping the replacement of an existing implicit local address if called via mptcp_pm_nl_get_local_id. Cc: stable@vger.kernel.org Fixes: d045b9eb95a9 ("mptcp: introduce implicit endpoints") Suggested-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Krister Johansen <kjlx@templeofstupid.com> --- v2: - Switch from call_rcu to skipping replacement if invoked via mptcp_pm_nl_get_local_id. (Feedback from Paolo Abeni) --- net/mptcp/pm_netlink.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) base-commit: 384fa1d90d092d36bfe13c0473194120ce28a50e